How do I identify an ERC-1967 contract?

Question

I understand both how to read the _IMPLEMENTATION_SLOT and how to get the implementation address of a proxy, provided I know the contract is a proxy.

What I'm wondering is: how do I determine if any given contract is an ERC-1967 provided just the contract address and the ABI?

For example, the Supepe contract is a transparent proxy and doesn't have an implementation(address) function. Without explicitly knowing that it is a transparent proxy, how would I determine that it is? I don't want to assume just because it has an Upgraded event that it's a proxy, since other contracts could have the same event without being a proxy.

Answer 1

ERC-1967 only standardizes storage slots. The ABI could be empty. You can read the implementation storage slot for that address, and if it has a non-zero value you can assume it's a proxy for most purposes.